The Corps will likely end the careers of roughly 40 percent of the active-duty lieutenants who come before thesecond of this year’s two career designation boards, slated to convene Aug. 6.

In all, 561 Marine officers will be considered by the board, according to a list of eligible lieutenants and captains published June 18 by Manpower and Reserve Affairs. Of those, at least 336 are likely to be selected, but that number could edge up toward 400 by the time the board’s final career designation rate is determined, based on the results of past boards and the assertion by Manpower and Reserve Affairs officials that career designation rates — which have hovered between 60 and 70 percent in recent years — should hold steady for the duration of the drawdown.

Career designation is a force-shaping tool the Corps uses to retain only the best-qualified officers and ensure the active-component officer population for each rank and year of service matches the promotion opportunities en route to major. It is one of most competitive processes in a junior officer’s career. Those selected are likely to have careers through retirement, if they remain in good standing.

At the first career designation board of fiscal 2013, held in February, 492 of the 809 officers considered were selected — a rate of 61 percent. The first and second boards of fiscal 2012 selected 62 percent and 68 percent of the lieutenants considered, respectively, a total of 1,274 officers.

This year, fewer than 900 will likely make the cut, but that is due, in large part, to declining manpower levels. Designation rates — the percentage of eligible Marines selected for a career — will remain relatively unchanged.

The picture has worsened slightly for officers in some communities, however. The boards consider Marines in one of five categories: combat arms, combat service support, aviation support, law and aviation. In 2011, 65 percent of the officers in combat service support, combat arms and aviation support received career designation. Law and aviation Marines were all qualified. In 2012, the designation rates dropped to 60 percent except for law and aviation officers, who were designated at a rate of 85 percent and 95 percent, respectively. At the first fiscal 2013 board, selection rates for law and aviation officers held steady again, but other Marines were designated at a rate of 55 percent, the lowest since the boards began convening biannually in 2010. While the overall designation rate for the second board, and designation rates for each category, are still unknown, it is unlikely they will dip further, according to manpower officials.